C++: All boost path operations segfault (OSX / GCC)

Question

I am getting consistent segfaults with almost any operation I am trying to perform with boost path.

(Edit: It appears that all segfaulting functions are related to current_path())

Sample program:

#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/path.hpp>
#include <iostream>

using namespace std;
using namespace boost::filesystem;
using namespace boost::system;


int main(int argc, const char * argv[])
{
    error_code err;
    auto p = path("hello/../world");
    cout << p.string() << endl;
    path c = canonical(p, err);
    cout << c.string() << endl;
}

The above is just an example, the following also segfault:
auto p = current_path(err);

And:
auto p = initial_path(err);

Compiled with:
g++-4.9 -lboost_filesystem -lboost_system -std=c++11 main.cpp -o ./path-test

Output:

hello/../world
Segmentation fault: 11

Both GCC and Boost installed via Homebrew.

System specs:

OSX:   10.9.4
GCC:   4.9.1
Boost: 1.0.55_2

---

Edit:

Compiled with -g and installed a signal handler as per comment, output:

hello/../world
Segfault:
0   path-test                           0x000000010ea215b8 _Z7handleri + 28
1   libsystem_platform.dylib            0x00007fff8b9285aa _sigtramp + 26
2   ???                                 0x00007fff67bdf1a1 0x0 + 140734933889441
3   path-test                           0x000000010ea2196d _ZN5boost10filesystem9canonicalERKNS0_4pathERNS_6system10error_codeE + 69
4   path-test                           0x000000010ea21518 main + 138
5   libdyld.dylib                       0x00007fff832c35fd start + 1
6   ???                                 0x0000000000000001 0x0 + 1

Segfault signal handler (Taken from this question):

void handler(int sig)
{
    void *array[10];
    size_t size;

    size = backtrace(array, 10);

    fprintf(stderr, "Segfault:\n");
    backtrace_symbols_fd(array, size, STDERR_FILENO);
    exit(1);
}

Answer 1

You're mixing implementations of the C++ standard library.

Boost, when installed via brew will be compiled using clang++. This toolchain uses libc++ by default.

g++ insists on using it's own libstdc++ implementation.

These implementations are not binary compatible, which is where the problems are arising.

I extracted a fresh copy of boost into a subdirectory, did a:

$ ./bootstrap.sh --prefix=/usr/local/boost156 cxxflags="-arch i386 -arch x86_64" address-model=32_64 threading=multi macos-version=10.9 toolset=g++-4.8 stage

Then built-it (static only; there's a build issue where it can't make the dynamic libraries in this situation under OSX - ld complains that the -h option is not supported):

$ ./b2 --layout=tagged threading=multi link=static toolset=gcc-4.8

When I compiled your code (because of threading=multi, I had to add -mt to the link options):

$ g++-4.8 -g -std=c++11 -Iboost_1_56_0  -Lboost_1_56_0/stage/lib -lboost_filesystem-mt -lboost_system-mt main.cpp -o ./path-test
$ ./path-test
hello/../world

$

i.e. it worked just fine in this case.

What does this mean?

• C++ libraries on OSX are a complete PITA if you're trying to mix g++ and clang++
• because all clang++ code defaults to being built with libc++ you're going to have to have private copies of any c++ libraries if you intend to build them with g++
• homebrew is just following orders when it compiles with clang++

It's a mess, but if you stick to the <sarcasm>one true compiler</sarcasm>, then you'll be fine. TBH I prefer clang's error messages and the static analysis is excellent; but if you have to use g++, you'll have to keep private copies of any c++ libraries that you want to use, also compiled with g++.